Project 3: The majority of studies examining speech perception in cochlear implant recipients have emphasized performance outcomes, that is, how well linguistic messages are understood. These studies have demonstrated large individual differences in speech and language outcomes following cochlear implantation. The reasons for this variability are not well understood, in part because we know little about how cochlear implant recipients use information in the speech signal to arrive at the intended message. The primary goal of the proposed work is to examine the central perceptual and cognitive processes used during spoken language comprehension that may contribute to variation in performance. Using empirical techniques from basic science, the proposed work will examine mechanisms of lexical processing and perceptual learning in a variety of cochlear implant users, including a group of cochlear implant participants implanted with novel hearing-preservation electrodes. The proposed research further will examine whether differences in these perceptual processing mechanisms are associated with individual variations in cochlear implant outcomes. Across the sample, this work will examine how the nature of the auditory input (electric vs. acoustic plus electric) influences lexical access, perceptual normalization, and perceptual learning in adults and children with cochlear implants. In cooperation with Projects 1 (A+E), 2 (Speech/Language Outcomes), 4 (Electrophysiology) and 5 (Music), the relationship between performance on these process-based measures and performance on other auditory and cognitive tasks will be analyzed. The results should simultaneously extend basic psycholinguistic theory and inform the development of cochlear implant processing strategies, candidate selection and novel therapeutic interventions for cochlear implant users.